Resistance to race TTKSK of Puccinia graminis f. sp. tritici in Emmer wheat

Race TTKSK (Ug99) of Puccinia graminis f. sp. tritici is a serious threat to wheat production worldwide because of its wide virulence on many cultivars and rapid spread. Emmer wheat [Triticum turgidum L. subsp. dicoccon (Schrank) Thell.] is known to be a source of resistance to stem rust but has not been evaluated against race TTKSK. In attempts to identify and characterize stem rust resistance genes effective against race TTKSK at the seedling stage, we evaluated 359 accessions of emmer wheat with race TTKSK and other races with broad virulence. A high frequency (31.8%) of accessions were resistant to TTKSK at the seedling stage with low infection types ranging from 2 ⁼ to 2 ⁺. Thirty-seven accessions exhibited a resistant to moderately resistant response in Debre Zeit, Ethiopia, and St. Paul, MN, nurseries in 2010 and 2011. Studies were conducted to determine the inheritance of TTKSK resistance in five accessions at the seedling stage. Results from evaluating F ₂ and F _2:3 generations revealed that resistance was conferred by single genes. One additional gene effective against race TTTTF was identified in the resistant parents. Results from this study indicated that emmer wheat is a source of resistance to race TTKSK and may contribute novel resistance genes. Since emmer wheat shares the same genome as durum [Triticum turgidum subsp. durum (Desf.) Husn.] wheat and is in cultivated form, resistance genes should be easily transferred to durum wheat by conventional breeding approaches.